Carbon
Dioxide (CO2) for Euthanizing Mammalian Prey

A
Note from Melissa Kaplan: This is
an often debated subject in the rec.pets.herp newsgroup and other forums,
online and off. One such discussion on RPH prompted large-scale rodent
breeder David Parizek to research the matter further. What follows is
a copy of his post back to the newsgroup.

It must
be noted that use of CO2 gas is not suitable for euthanizing reptiles.

According to the American
Veterinary Medical Association's Panel on Euthanasia (Journal of the
AVMA, Vol. 202, No. 2, Jan. 15, 1993), the best (=most humane) way
to kill rats (and mice) that will be fed to other animals is to asphyxiate
(spelling?) them with carbon dioxide gas. Other gases (anesthetics) can
be good, but then there could be "accumulation of tissue residues
in food producing animals." (= not good to feed to your herps). The
report conditionally finds cervical dislocation to be an acceptable method
also, as long as the rats are small (less than 200 grams). Bonking, stunning,
etc. are specifically listed as NOT considered acceptable. They noted
that "data suggest that electrical activity in the brain persists
for 13 seconds following cervical dislocation." For this reason,
they consider the jury to still be out on the technique. My interpretation
is that this is the best technique if you don't have access to gaseous
CO2 -- like for the person who needs to kill only a few. However, dry
ice can be purchased for around $1.25 per pound at many ice cream shops/ice
retailers. If you use dry ice then make sure you don't touch it -- insulate
your hands with a towel or something. Similarly, you don't want the rodents
to touch it. You should pre-charge the container with the vaporizing dry
ice prior to introducing the animals to be euthanized, to make it maximum
quick, and to use enough gas -- as only high concentrations have the more
humane effects. If you have access to bottled CO2, this is even better.

I have used cervical dislocation
in the past on thousands of rodents. Now, since I was prompted to think
about the the issue further by my customers (and this thread), I asked
around and located the AVMA report, and I now use gaseous CO2 to euthanize
mice (I got a used 50 pound bottle and hose for $95 -- they are readily
available from fire extinguisher service companies). To me, I was skeptical,
but after actually trying it, it does appear to be more humane. The key
is to pre-prime the container with the gas, to not agitate them ahead
of time (AVMA recommends a quiet setting -- part of what is implied in
humane is to avoid stressing the animals). I was surprised and impressed
to be honest. I guess, IMHO, that part of the problem with the other techniques
is that it is often imprecise. Cervical dislocation usually works well,
but the technique actually takes some practice and it doesn't always go
perfectly. The CO2 method is humane -- the CO2 method has a "rapid
depressant and anesthetic effect" when inhaled in high concentrations.
It is not instantaneous, but it is surprisingly fast, and the rodents
don't appear to be in pain.